It is strongly requested in recent years that portable communication terminals are miniaturized and power consumption thereof is reduced in mobile communication systems of a cellular phone and the like. In order to realize the above, for example, an on-resistance Ron should be reduced concerning an antenna switch. As one of semiconductor devices in practical use for the antenna switch, there is a junction field-effect transistor (JPHEMT: junction pseudo-morphic high electron mobility transistor).
JPHEMT is a semiconductor device performing current modulation by using a p-n junction and a hetero junction. The semiconductor device of this type has the hetero junction of a channel layer made of, for example, InGaAs and a barrier layer (AlGaAs) made of AlGaAs having a wider bandgap than the channel layer (InGaAs). A low-resistance region including an impurity is provided in a surface layer in the barrier layer (AlGaAs) opposite to the channel layer, and a gate electrode is connected to the low-resistance region. A source electrode and a drain electrode are Ohmic-connected on the barrier layer at both sides of the low-resistance region and the gate electrode.
In the semiconductor device having the above structure, a two-dimensional electron gas layer in which electrons to be carriers are shut with high concentration is formed in an interface on the barrier layer's side in the channel layer. Then, current flowing between the source electrode and the drain electrode is modulated through a channel-layer portion below the low-resistance region by controlling the concentration of the two-dimensional electron gas layer using a gate voltage (see, for example, JP-A-11-150264 (Patent Document 1)).